1. Field of the Invention
The present invention relates to a friction agitation joining method for joining metallic members such as aluminum or its alloy members butted against each other. More particularly, the present invention relates to a friction agitation joining method for use in manufacturing, for example, tailored blank members, suspension arm members or engine mount members for automobiles, body panels for railroad vehicles and/or vessels, and electric mechanical members.
2. Description of Related Art
A friction agitation joining method belongs to a category of a solid-phase joining method. The friction agitation joining method has such advantages that it can be applied to various metal joining members regardless of the materials and that joining members are hardly deformed by thermal strains at the time of joining. Thus, in recent years, the method has been used for joining various structural members.
FIG. 5A shows two pieces of plate-like metal joining members butted against each other to be joined by a friction agitation joining method.
In FIG. 5A, the reference numeral xe2x80x9c51xe2x80x9d denotes a thicker plate-shaped metal first joining member and xe2x80x9c52xe2x80x9d a thinner plate-shaped metal second joining member. These joining members 51 and 52 are arranged such that the lateral side surfaces thereof are butted against each other with the lower surfaces thereof flush with each other. Thus, a level difference corresponding to the thickness difference thereof is formed at the upper surface sides thereof. The reference numeral xe2x80x9c55xe2x80x9d denotes a butted portion of the joining members 51 and 52. The reference numeral xe2x80x9c54xe2x80x9d denotes a stepped portion formed at the butted portion 55 on the upper surface sides of the joining members 51 and 52.
In FIG. 5B, the reference letter xe2x80x9cAxe2x80x2xe2x80x9d denotes a joining device for performing a but-joining. This joining device Axe2x80x2 is comprised of a joining bed 80 (see FIG. 5A), a joining tool 60 for performing a friction agitation joining and an elevator 70.
The joining bed 80 is arranged such that the upper surface 81 thereof is disposed horizontally. On this upper surface 81, both the aforementioned joining members 51 and 52 are placed with their upper surfaces thereof facing up. In these joining members 51 and 52, the first joining member 51 corresponds to a joining member having a higher upper surface level as seen from its surface side, and the second joining member 52 corresponds to a joining member having a lower surface level as seen from its surface side.
The elevator 70 is arranged above the joining members 51 and 52 and capable of ascending and descending vertically.
The joining tool 60 having a rotation axis Qxe2x80x2 is provided with a pillar-like rotor 61 having a larger diameter and formed about the rotation axis Qxe2x80x2 and a pin-like probe 62 having a smaller diameter and integrally protruded from the rotation central portion of the end surface 61a of the rotor 61 along with the rotation axis Qxe2x80x2. This joining tool 60 is equipped to a rotation driving apparatus (not shown) for rotating the rotor 61 and the probe 62 about the rotation axis Qxe2x80x2. In the joining tool 60, the peripheral edge of the end surface 61a of the rotor 61 is placed within the plane perpendicular to the rotation axis Qxe2x80x2. As shown in FIG. 5B, the end surface 61a of the rotor 61 is formed to have a flat surface perpendicular to the rotation axis Qxe2x80x2.
By the way, in cases where both the butted joining-members 51 and 52 are joined in a state that the stepped portion 54 is formed on the upper surfaces thereof, stress concentration will generate in the stepped portion 54 of the obtained joined portion, resulting in deteriorated strength reliability. Moreover, during the joining process, some materials of the joining members 51 and 52 softened by the frictional heat disperses from near the probe 62, resulting in joint defects due to insufficient materials.
It is an object of the present invention to provide a friction agitation joining method which is favorably used for joining two plate-shaped joining members butted against each other such that a level difference is formed at upper surface sides thereof.
It is another object of the present invention to provide a friction agitation joining method which can enhance the joining operation efficiency of the aforementioned butted joining members.
Another objects of the present invention will be apparent from the following embodiments of the present invention.
In order to attain the aforementioned objects, according to the present invention, a friction agitation joining method for joining two plate-shaped joining members butted against each other with a level difference formed at upper surface sides thereof by utilizing a joining tool having a probe rotatable about a rotation axis thereof, comprising the steps of:
arranging the butted joining members so as to be inclined to a horizontal plane with one of the joining members having a higher upper surface level positioned at a lower side and the other of the joining members having a lower upper surface level positioned at a higher side;
inserting the probe rotating about the rotation axis into a butted portion of the butted joining members or the vicinity thereof in a state that the rotation axis is parallel to a vertical plane extending along the butted portion; and
moving the probe relative to the joining members along the butted portion with the probe inserted into the butted portion or the vicinity thereof.
According to the aforementioned friction agitation joining method, by downwardly moving the joining tool in the vertical direction, the probe can be quickly inserted into the butted portion of the joining members or its vicinity. This increases the insertion speed of the probe, resulting in enhanced joining operation efficiency.
It is preferable that the step of inserting the probe is performed in a state that the rotation axis is disposed vertically. In this case, the probe can be inserted more quickly. This further increases the probe insertion speed, resulting in further enhanced joining operation efficiency. Furthermore, as compared to the case where the joining tool is inclined so that the probe can be inserted into the butted portion of the joining members in an inclined state, it becomes possible to prevent the inclination of the joining tool due to the influence of gravity because the rotation axis of the probe is disposed vertically. Accordingly, a joined member with an excellent joined portion can be obtained.
Furthermore, it is preferable that the joining tool is attached to an elevator disposed above the butted joining members and capable of ascending and descending vertically and that the step of inserting the probe is performed by descending the elevator. In this case, the insertion of the probe can be performed with high efficiency by utilizing the elevator without attaching any additional device for inserting the probe.
Furthermore, it is preferable that the joining tool is provided with a rotor having a diameter larger than a diameter of the probe protruded from a part of an end surface of the rotor, the rotor being capable of rotating about the rotation axis, and that the step of moving the probe relative to the joining members is performed in a condition that the end surface of the rotor rotating about the rotation axis presses a shoulder portion of one of the joining members having a higher upper surface level formed at the butted portion. In this case, since the end surface of the rotor presses the shoulder portion of one of the joining members having a higher upper surface level formed at the butted portion, the shoulder portion will be plastically deformed into an inclined surface due to the pressing force. Consequently, stress concentration, which may be generated at the stepped portion, can be reduced.
Furthermore, it is preferable that the end surface of the rotor vertically presses the shoulder portion. In this case, the shoulder portion can be plastically deformed quickly, resulting in enhanced joining operation efficiency.
Furthermore, it is preferable that the joining tool is equipped to an elevator disposed above the joining members and capable of ascending and descending vertically and that the end surface of the rotor presses the shoulder portion by descending the elevator. In this case, pressing the shoulder portion can be performed with high efficiency by utilizing the elevator without attaching any additional device for pressing the shoulder portion.
Furthermore, it is preferable that the joining members are arranged so as to be inclined at from 3xc2x0 to 45xc2x0 to a horizontal plane. If the angle to a horizontal plane is less than 3xc2x0, it becomes difficult to deform the shoulder portion of one of the joining members having a higher surface level. On the other hand, if the angle exceeds 45xc2x0, the edge of the rotor comes into contact with the surface of the other of the joining members having a lower surface level, which may prevent the insertion of the probe into the butted portion or its vicinity. Accordingly, it is preferable that the joining members are arranged so as to be inclined at from 3xc2x0 to 45xc2x0 to a horizontal plane, more preferably from 5xc2x0 to 10xc2x0 to a horizontal plane.
Furthermore, it is preferable to provide a stand having an upper surface inclined to a horizontal plane, and the joining members are arranged on the inclined upper surface of the stand to thereby be inclined to a horizontal plane. This enhances the inclined arrangement of the joining members.
Furthermore, it is preferable that the probe is rotated at a rotation speed of from 1000 rpm to 3000 rpm.
Furthermore, it is preferable that one of the joining members having a higher upper surface level is thicker than the other of the joining members having a lower upper surface level, and wherein the one of the joining members having a higher upper surface level and the other of the joining members having a lower upper surface level are butted against each other with bottom surfaces thereof flush with each other.